Automatic multirange display apparatus and control therefor

ABSTRACT

Digital data which is arithmetically processed in &#39;&#39;&#39;&#39;floating point&#39;&#39;&#39;&#39; computation is displayed using mantissa and exponent notation. Automatic ranging according to the exponent provides a display which assures optimum resolution, and hysteresis control over the automatic ranging eliminates undesirable range changing on display data which varies only slightly beyond a range limit.

United States Patent 1151 3,697,960 Gordon Oct. 10, 1972 [54] AUTOMATIC MULTIRANGE DISPLAY 3,056,550 10/1962 Horrell ..235/164 APPARATUS AND CONTROL 3,l03,580 9/ 1963 Foreman ..235/ l 59 THEREFOR 3,389,379 6/1968 Erickson et al ..340/l 72.5 [72] Inventor: Gary B. Gordon, Cupertmo, Callf. Primary Emminer Harvey E springbom [73] Assignee: Hewlett-Packard Company, Palo An A, C, Smith Alto, Calif.

22 Filed: Feb. 16, 1971 1571 ABSTRACT Appl. No.: 115,795

Related U.S. Application Data Continuation of Ser. No. 799,717, Feb. I7, 1969, abandoned.

U.S. Cl. .340/l72.5 Int. Cl ..G06f 3/14 Field of Search ...340/l72.5; 235/l55, 157, 159,

References Cited UNITED STATES PATENTS 6/1962 Sierra ..235/1 59 4 Claims, 1 Drawing Figure IOST SICIIIFIGIIT MIT 53 55 PREFIX umrs 3o 7:. s? as g 57 59 -5o EXPOHENT DISPLAY i "33 DETECRZ 43 45 4? 1.0011; A A

1 l l l l l l l l l l l l 1 aurrea Burris aurrra aurrsn aurrsn STEERlNG (0R SHlFTlNG) LOBIC conrurso T EXPOHENT a 23 n a 13 15 (I? 19 DATA PROCESSlNG UNlT 27 l l l I DI'SPLAY 0m Tmmc CONTROL 2e: INPUT CROSS-REFERENCE TO RELATED APPLICATION This is a continuation application of U.S. Pat. application Ser. No. 799,717, entitled DIGITAL MUL- TIRANGE DISPLAY APPARATUS HAVING HYSTERESIS IN THE RANGE CONTROL filed Feb. 17, 1969, by Gary B. Gordon, now abandoned.

BACKGROUND OF THE INVENTION Certain known digital data-handling devices compute numerical data using mantissa and exponent notation of the number to be computed and then display the results of the computation in either fixed point or floating point notation. Devices of this type are described in the literature (see, for example Hewlett-Packard Company Journal, Vol. 20, No. I, September 1968).

It is frequently desirable to display numerical data using floating point notation because the number of bits or digit places required to display large numbers may be substantially smaller than the number of bits or digit places required to display similar large numbers in fixed point notation, as shown in the examples below. In fixed point notation, numerical data may be displayed as follows:

l0.20304 The same numerical data may be displayed in floating point notation as follows:

I .020304 +1 where for each floating point number the grouping of digits about the decimal point is referred to as the mantissa and the digit to the right of the mantissa is the power to which the mantissa multiplier of must be raised to define the number and is referred to as the exponent.

For displays on specialized digital devices such as voltmeters, frequency meters, or the like, the exponent may also be described using common prefixes in place of the exponent numbers, for example, kilo in place of+3 (or 10), mega" in place of+6 (or 10), milli" in place of 3 (or 10'), or micro in place of-6 (or 10*). Numerical data displayed using this hybrid type of notation tends to be more readily understandable and more clearly dissociates the exponent from the mantissa. However, numerical displays that use such prefix designations of the exponent in floating point notation have the limitation that range changes commonly occur in steps of 1,000, for example, from kilo" (or +3) to mega (or +6). Where automatic ranging is provided, the numerical display may jump around undesirably between two ranges as the numerical data varies about the limit between the two ranges, as shown below:

1.0000 Mega (ohms, Hertz, volts, or the like) 999.99 Kilo (same) 1.0000 Mega (same) In these conditions, it is usually undesirable to change ranges because the simultaneous change of prefix and shift in position of the digits with respect to the decimal point makes the display difficult to read.

SUMMARY OF THE INVENTION Accordingly, the present invention introduces hysteresis in the automatic range-changing of numerical data display so that numerical data may be displayed, for example, in the higher range as the data varies slightly below the range limit to the next lower range, as shown below:

1.0000 Mega (ohms, Hertz, volts, or the like) .9999 Mega (same) 1.0000 Mega (same) This is accomplished by detecting the most significant digit or digits of upcoming data to be displayed, by detecting the displayed most significant digit or digits and by inhibiting the automatic range-changing circuitry in response to a selected combination of these detected conditions.

DESCRIPTION OF THE DRAWING The drawing is a schematic diagram of the display apparatus according to the present invention which operates with conventional data processing means to display numerical data in floating point notation with hysteresis control of automatic ranging.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, there is shown conventional data processing means 9 such as a counter, calculator, computer, or the like that includes bit registers 11-19 which form the portion of the data processing means 9 that attains logic states indicative of a data computation that is to be displayed. The bit registers 11-19 are shown spatially separated within the processing means for clarity, but it should be understood that these bit registers may in general be any suitable logic elements within digital signal processing apparatus where the logic elements have operating states that are representative of numerical data which is to be displayed. Data processing means of this type are described in the literature (see, for example, U.S. Pat. application Ser. No. 559,887, entitled SIMPLIFIED RACE-PREVENTING FLIP-FLOP HAVING A SELECT ABLE NOISE IMMUNITY THRESHOLD, filed on June 23, 1966 by Thomas E. Osborne, now issued as U.S. Pat. No. 3,566,160 and U.S. Pat. No. 3,388,385, entitled NONDESTRUCT IVE ROUND- OFF DISPLAY CIRCUIT issued on June 1 l, 1968 to Joseph A. Lukes). The data processing unit 9 operates under the control of a local clock or timing control 21 to provide numerical data for display at the end of a calculation or other logic operation in the tom of separate mantissa present in bit registers 11-19 and separate exponent present on output line or lines 23. The data calculation assumes that a decimal point 25 is located after a selected bit register, say the most significant bit register, and the exponent signal on output line 23 is calculated accordingly. Also, the data processing unit 9 may provide an end-of-calculation signal on line 27 after a data calculation is completed and this signal actuates timing control 21 to initiate a display of the results of the data calculation or other logic operation.

In normal operation when the results of a data calculation are well within the limits of a given range, the signal on line 29 from timing control 21 which initiates a display activates the display logic 30 to transfer the mantissa in bit registers 1 1-19 into display buffer stages 31-39. The buffer stages 31-39 into which the digits of the mantissa are transferred are selected with respect to any one of the display decimal (or other radix) points 4347 in accordance with the exponent signal on line 23. The numerical data in bit registers 11-19 may be transferred to the selected buffer stages 31-39 by simultaneous, parallel transfer through the logic means 49 or by serial transfer through logic means 49 in a manner commonly associated with circulation of numerical data between shift registers. The buffer stages 31-39 may include decoding logic for converting signals used in the data calculation, for example, binary signals, to other suitable output signals such as l-line decimal code, or the like, which provides a useful output manifestation of the data calculation. The bufier stages 31-39 may also provide display storage of the numerical data transferred thereto from the bit registers 11-19 for maintaining a constant output while the bit registers 11-19 are used for new data calculations.

The logic means 49 selectively steers the parallel transfers (or shifts the serial transfers) from the bit register to the appropriate buffer stages under the control of the display logic circuit 30 which, in turn, responds to the exponent signal that appears on line 23 at the end of a calculation. For example, if the mantissa and exponent of a numerical calculation in the data processing unit are:

then the data manifestation representing 4 in bit register 11 may be transferred to buffer stage 31 and the data manifestation representing 6 in bit register 13 may be transferred to buffer stage 33. Similarly, the data manifestations representing the numbers 7, 8 and 9 of the mantissa appearing in the remaining bit registers l5, l7 and 19 may be transferred, respectively, to the buffer stages 35, 37 and 39. The location of the decimal point in the display in general does not have to coincide with the assumed location of the decimal point in the data processing unit but may be displayed in any location, say, 43, 45 or 47 in combination with the prefix displayed by the output means 50. Thus the number in the above example may be displayed for visual readout on the alphanumeric display apparatus 51-59 coupled to the buffer stages 31-39 as follows:

0.4678 Mega (volts, Hertz, or the like) 467.89 Kilo (same) in the first display example above, the display decimal point may be illuminated or otherwise displayed at location 43 with the prefix mega" (or l0") displayed by means 50. Also, in the second display example above, the display decimal point may be illuminated or other wise displayed at location 47 with the prefix kilo" (or displayed by means 50. It is apparent from these two examples that the display decimal point may be located wherever convenient, independent of the location assumed for the decimal point in the data calculation performed by the processing means 9. However, it is also apparent that greatest resolution of display is derived from maintaining the numerical data maximally shifted to the most significant digit position so that the display apparatus 51-59 is filled with the significant digits of the numerical data. For this reason, other display units in special applications may require the use of decimal points located at other positions such as 43, 45 or 47. The particular location in the display apparatus 51-59 of digits of numerical data and the location of the decimal point in the display and the prefix units in means 50 are thus all controlled by the display logic 30 in response to the exponent signal appearing on line 23.

When the numerical data to be displayed is close to the limits of a given display range (say, kilo or mega), automatic range-changing of the prefix units displayed by means 50 and the shifting of the location of the display decimal point may be unnecessarily confusing and therefore undesirable in certain circumstances. in accordance with the illustrated embodiment of the invention, hysteresis is introduced into the range-changing limits so that a lower-value number may be displayed on the next higher range. As used herein, the term hysteresis" refers to the ordinary meaning of the difference between the response of the system to increasing and decreasing values. This is accomplished by inhibiting the display logic 30 from introducing a range change in response to the occurrence of a selected data manifestation upcoming from bit register 11 after data is processed or calculated, or the like, in processing means 9 and to the occurrence of selected display digits in the most significant place or places. The detector 61 produces an output on line 63 in response to the appearance of an upcoming data manifestation in bit register 11 that represents the digit 9. It should be understood, however, that any digit for display other than 9 may be selected as the lower limit of hysteresis in the changing of ranges. in the illustrated embodiment, detector unit 65 determines whether the displayed digit in the most significant place is less than 2 (ie is l (i.e. or 0) and produces an output on line 67 when such condition is satisfied. it should be understood, however, that the upper limit at which hysteresis may be introduced may be selected to be other than less than 2. Also, it should be understood that the hysteresis logic 73 may itself be coupled to the input for the most significant mantissa digit and be arranged to store the displayed digit and respond when the displayed digit is less than 2 (i.e. either 1 or 0) and the upcoming digit to be displayed is 9.

The signals on lines 63 and 67 are combined in a suitable logic circuit within hysteresis logic 73 to inhibit the display logic 30 from introducing a range change when both signals on these lines are present. This means that if a displayed digit has a value between l.9999 and l.0000 and the upcoming digits to be displayed are between .99999 and .90000, the hysteresis logic supplies an inhibit signal to display logic 30 which is thereby inhibited from altering the displayed prefix 50 and from altering the location of the decimal point 43, 45 or 47. Numerical data which decreases gradually in value in successive displays will thus be displayed as follows:

2.5000 Mega (ohms, Hertz, volts, or the like) l.8000 Mega (same) 1.1000 Mega (same) .9400 Mega (same) .9100 Mega (same) 870.00 Kilo (same) Numerical data which decreases rapidly in successive displays from a value above the upper limit (here, lr9999) at which hysteresis may be introduced is dis played as follows:

2.5000 Mega (ohms, Hertz, volts, or the like) 940.00 Kilo (same) 870.00 Kilo (same) When the most significant displayed digit is 0, the present circuit is operating in the hysteresis range and a subsequent data manifestation which satisfies the hysteresis conditions (i.e. the most significant display digit is l or and the upcoming digit to be displayed is 9) maintains the operation in the hysteresis range.

Numerical data which increases in value in successive displays produces a range change that is uninhibited by the hysteresis logic 73 (because the display condition determined by detector unit 65 does not occur) and is displayed as follows:

870.00 Kilo (ohms, Hertz, volts, or the like) 940.00 Kilo (same) I .1000 Mega (same) l.8000 Mega (same) It should be noted from these examples of successive displays that the logic means 49 which is controlled in response to the output of hysteresis logic 73 transfers the digits of the mantissa in bit registers 11-49 into the proper buffer stages 31-39 and associated display means 51-59 shifted one or more places to the left or right and that the display logic 30 also determines the location of the decimal point 43, 45 or 47 and the proper prefix units 50 to be displayed.

Therefore, the present invention responds to gradual decreases of displayed digital data to provide hysteresis control over automatic range changing in apparatus which includes digital output means. The proper range is selected after each manipulation of digital data and before each display of the upcoming digits so that each data manipulation may be properly displayed without requiring conventional over-range adjustment that is typically useful only for a subsequent data manipulation and display.

I claim:

1. The method of displaying in selected digit places each of successive data signals represented by mantissa and exponent values, the method comprising the steps of:

establishing a first logic condition representative of the most significant mantissa digit of a displayed data signal attaining a value less than a first predetermined value;

establishing a second logic condition representative of the most significant mantissa digit of a data signal to be displayed attaining a second predetermined value;

displaying the most significant mantissa digit of the data signal to be displayed shifted to a less significant digit place than the most significant digit place and displaying successively less significant mantissa digits of the data signals to be displayed correspondingly shifted to less significant digit places in response to the simultaneous occurrence of the first and second logic conditions; and producing an output indication representative of an exponent value higher than the exponent value of the same data signal to be displayed in response to the simultaneous occurrence of the first and second logic conditions.

2. Digital data apparatus including a data processing unit for processing applied data signals to provide mantissa digit output signals and exponent output signals representative of processed data signals, the apparatus comprising:

a plurality of output means for providing an output indication of at least the most significant mantissa digit in a selected one of the output means;

indicator means for providing an output indication representative of an exponent output signal;

circuit means connected to said output means for applying mantissa output signals representing at least the most significant mantissa digit to selected ones of said output means in response to a control signal applied thereto;

logic means responsive to an output indication by the output means of a mantissa digit in a selected significant digit place and having a logic state representative of the output indication in said selected digit place of a mantissa digit being less than a first predetermined value;

detector means coupled to receive the mantissa output signals and responsive to the appearance of a mantissa output signal representative of the most significant mantissa digit of second predetermined value for producing a detector output signal indicative of the appearance of a mantissa digit of said second predetermined value; and

control means coupled to receive the detector output signal and the exponent output signal associated with a processed data signal and responsive to the logic state of said logic means for producing a plurality of outputs, one of the outputs being a control signal supplied to said circuit means to apply the mantissa output signal representing the most significant mantissa digit of the same processed data signal to a selected one of said output means, and another of said outputs of the control means actuating said indicator means to provide an output indication of an exponent value that is different from the exponent value represented by said exponent output signal of the same processed data signal.

3. Digital data apparatus as in claim 2 wherein:

said circuit means includes signal transfer circuits which are responsive to said control signal applied thereto for applying the mantissa output signal representing the most significant mantissa digit of a processed data signal to the output means which is disposed to provide an output indication of the next most significant digit; and

said control means includes a logic circuit which ac tuates said indicator means to provide an output indication representative of the exponent output signal for the same processed data signal that is higher than the exponent value represented by said exponent output signal.

4. Digital data apparatus as in claim 2 wherein said control means includes a logic circuit responsive (a) to said logic state of the logic means which is indicative of the output indication of the most significant mantissa digit provided by said output means being less than 2 and (b) to a mantissa output signal representing the digit and actuating said indicator means to provide an output indication of an exponent value higher at least by one than the value represented by the exponent output signal associated with the same processed data signal. 

1. The method of displaying in selEcted digit places each of successive data signals represented by mantissa and exponent values, the method comprising the steps of: establishing a first logic condition representative of the most significant mantissa digit of a displayed data signal attaining a value less than a first predetermined value; establishing a second logic condition representative of the most significant mantissa digit of a data signal to be displayed attaining a second predetermined value; displaying the most significant mantissa digit of the data signal to be displayed shifted to a less significant digit place than the most significant digit place and displaying successively less significant mantissa digits of the data signals to be displayed correspondingly shifted to less significant digit places in response to the simultaneous occurrence of the first and second logic conditions; and producing an output indication representative of an exponent value higher than the exponent value of the same data signal to be displayed in response to the simultaneous occurrence of the first and second logic conditions.
 2. Digital data apparatus including a data processing unit for processing applied data signals to provide mantissa digit output signals and exponent output signals representative of processed data signals, the apparatus comprising: a plurality of output means for providing an output indication of at least the most significant mantissa digit in a selected one of the output means; indicator means for providing an output indication representative of an exponent output signal; circuit means connected to said output means for applying mantissa output signals representing at least the most significant mantissa digit to selected ones of said output means in response to a control signal applied thereto; logic means responsive to an output indication by the output means of a mantissa digit in a selected significant digit place and having a logic state representative of the output indication in said selected digit place of a mantissa digit being less than a first predetermined value; detector means coupled to receive the mantissa output signals and responsive to the appearance of a mantissa output signal representative of the most significant mantissa digit of second predetermined value for producing a detector output signal indicative of the appearance of a mantissa digit of said second predetermined value; and control means coupled to receive the detector output signal and the exponent output signal associated with a processed data signal and responsive to the logic state of said logic means for producing a plurality of outputs, one of the outputs being a control signal supplied to said circuit means to apply the mantissa output signal representing the most significant mantissa digit of the same processed data signal to a selected one of said output means, and another of said outputs of the control means actuating said indicator means to provide an output indication of an exponent value that is different from the exponent value represented by said exponent output signal of the same processed data signal.
 3. Digital data apparatus as in claim 2 wherein: said circuit means includes signal transfer circuits which are responsive to said control signal applied thereto for applying the mantissa output signal representing the most significant mantissa digit of a processed data signal to the output means which is disposed to provide an output indication of the next most significant digit; and said control means includes a logic circuit which actuates said indicator means to provide an output indication representative of the exponent output signal for the same processed data signal that is higher than the exponent value represented by said exponent output signal.
 4. Digital data apparatus as in claim 2 wherein said control means includes a logic circuit responsive (a) to said logic state of the logic means which is indicative of the output indication Of the most significant mantissa digit provided by said output means being less than 2 and (b) to a mantissa output signal representing the most significant mantissa digit of a processed data signal being equal to 9 to apply control signal to said circuit means, said circuit means applying the mantissa output signal representing the most significant mantissa digit of a processed data signal to the output means which is disposed to provide an output indication of a mantissa digit less significant than said most significant digit and actuating said indicator means to provide an output indication of an exponent value higher at least by one than the value represented by the exponent output signal associated with the same processed data signal. 